Water ballast arrangement for externally insulated tankers

ABSTRACT

An arrangement of internal water ballast tanks for an externally insulated tanker wherein the ballast tanks are suitably sized and located within the cargo carrying midbody of the tanker so as to permit loading a quantity of sea water ballast to provide for satisfactory operation and sea kindliness of the ship. The ballast tanks preferably have a cylindrical configuration and are built into the internal structure of the ship. The tanks are insulated on the water side so that the tank structure will be at the same temperature as the adjacent ship structure, and are connected with suitable ballast loading and discharge facilities.

United States Patent Cowles WATER BALLAST ARRANGEMENT FOR EXTERNALLY INSULATED TANKERS [75] Inventor: Walter C. Cowles, Cobham,

England [73] Assignee: Esso Research and Engineering Company, Linden, NJ.

[22] Filed: Nov. 22, 1971 [21] Appl. No.: 200,984

[52] US. Cl 114/74 A [51] Int. Cl B63b 25/08 [58] Field of Search 114/74 R, 74 A [56] References Cited UNITED STATES PATENTS 1.148.822 8/1915 Bittlestone et al. 114/74 R 1.187.951 6/1916 White 114/74 R 3.283.734 11/1966 Gorman 114/74 A 3.052.203 9/1962 Henry 114/74 A FOREIGN PATENTS 0R APPLICATIONS 246.441 9/1925 Great Britain 114/74 R 925,271 8/1961 Great Britain 114/74 R Primary Examiner-Trygve M. Blix Assistant Examiner-Stuart M. Goldstein Attorney, Agent, or Firm-F. D. Paris; D. F. Wohlers [57] ABSTRACT An arrangement of internal water ballast tanks for an externally insulated tanker wherein the ballast tanks are suitably sized and located within the cargo carrying midbody of the tanker so as to permit loading a quantity of sea water ballast to provide for satisfactory operation and sea kindliness of the ship. The ballast tanks preferably have a cylindrical configuration and are built into the internal structure of the ship. The

tanks are insulated on the water side so that the tank structure will be at the same temperature as the adjacent ship structure, and are connected with suitable ballast loading and discharge facilities.

9 Claims, 6 Drawing Figures WATER BALLAST ARRANGEMENT FOR EXTERNALLY INSULATED TANKERS BACKGROUND OF THE INVENTION Previously there has been disclosed in the US. Gorman US. Pat. No. 3,283,734, assigned to the assignee of the present invention, an externally insulated tanker for the transportation of liquefied natural gas (LNG) and other low (or high) temperature liquids. The design of an externally insulated cryogenic tanker (EICT) is such that the cargo is contained by the hull structure. In conventional tankers the cargo tanks are employed alternately as ballast tanks. In prior cryogenic tankers, the cargo is carried in independent cargo tanks and ballast tanks are incorporated in the double hull structure. In the EICT concept, the entire cargo section is at cryogenic temperature and thus, unsuitable for the containment of water ballast. Accordingly, it is necessary to provide a suitable ballast arrangement for externally insulated tankers in order to provide suitable immersion for the propeller, to make the ship manageable in varying winds, to avoid slamming, and generally to provide for satisfactory operation of the tanker in its unloaded condition.

SUMMARY OF THE INVENTION The present invention provides a novel internal ballast arrangement for an externally insulated tanker wherein internal water ballast tanks are incorporated into the internal structure of the vessel. In a preferred embodiment of the present invention the internal water ballast tanks are vertically oriented and have a cylindrical configuration. In one embodiment the ballast tanks are located at the intersection of each of the transverse bulkheads with the main longitudinal bulkhead of the ship within its cargo carrying midbody. Insulation on the internal or water side of ballast tanks permits the tank structure to be at the same temperature as that of the adjacent ship structure. This prevents the occurrence of any problem of differential thermal contraction. Alternate embodiments comprise construction of the ballast tanks between each of the cargo tank bulkheads and an adjacent web frame. Other modifications include disposing the cylindrical ballast tanks in a horizontal position.

Accordingly, it is a primary object of the present invention to provide a novel internal water ballast tank arrangement for a ship.

A further object of this invention is to provide a novel internal water ballast arrangement for an externally insulated tanker.

Having in mind the above and other objectsand advantages that will be apparent from an understanding of this disclosure, the present invention comprises the combination and arrangements as illustrated in the preferred embodiments of the invention which are hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction, and advantages thereof when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic profile view of an externally insulated tanker incorporating an internal water ballast arrangement according to the present invention;

FIG. 2 is a schematic top plan view of the externally insulated tanker of FIG. 1;

FIG. 3 is an enlarged vertical cross'sectional view taken substantially along the line 3--3 of FIG. 1 illustrating the overall arrangement of a cylindrical watter ballast tank incorporated into the internal ship structure;

FIG. 4 is an enlarged vertical cross-sectional view taken substantially along the line 4-4 of FIG. 3 illustrating in detail the water ballast tank construction;

FIG. 5 shows an alternate arrangement and construction for internal water ballast tanks; and

FIG. 6 shows a schematic top plan view of the embodiment of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Having reference to the drawings wherein like parts are designated by the same reference numeral throughout the several views, the present invention is illustrated as embodied in an externally-insulated tanker suitable for the transportation of LNG or other low temperature liquids. Typically, such a tanker would have a cargo-carrying midbody constructed of 9 percent nickel steel, reference being made to the aforementioned Gorman U. S. Pat. No. 3,283,734 for a more detailed explanation thereof. As shown, the tanker generally designated 10, includes a forward hull portion or bow 12, an after hull portion or stem 14 and a cargo section 16. The bow and stem are fabricated conventionally from mild steel plate and mild steel strengthening members. The cargo-carrying midbody 16 may be connected between the bow and stern as disclosed in copending U. S. Pat. No. 3,671,315, assigned to the same assignee as that of the present application. Preferably, the midbody 16 is fabricated from a material possessing physical and mechanical properties compatible with the particular cargo to be carried, which, in the present case, would be LNG or some other low temperature cargo. A suitablematerial would be 9 percent nickel steel. A main central longitudinal bulkhead 18 divides the vessel longitudinally into port and starboard cargo holds. A plurality of transverse bulkheads 20 are spaced longitudinally throughout the midbody to divide the port and starboard cargo holds into cargo-carrying compartments 22. The alloy steel shell of the midbody 16 is completely enveloped or clad externally with asuitable thermal insulation material 24. Reference is made to copending U. S. Patent Application Ser. No.

System for External Insulation, assigned to the same assignee as that of the present application, for specific details as to a suitable manner in which the insulation may be secured to the hull of the ship. Preferably, the external insulation is provided with an outer protective coating 26 to prevent damage to the insulation either when it comes in contact with another physical body or from its normal association with the water. (See FIG. 4.)

As shown in FIGS. 1 and 2, there is provided an internal water ballast arrangement comprising a plurality of cylindrical-shaped ballast tanks 28. These tanks are disposed vertically between the deck and bottom of the hull and are located at the intersection of each of the transverse bulkheads 20 with the main longitudinal bulkhead 18. The top and bottom of each ballast tank comprises a truncated-conical configuration terminating in a relatively narrow duct 30 and 46 which are connected in an operable manner with suitable ballast handling (for ballast loading and discharge) arrangements. Each ballast tank includes an internal layer of insulation 32 and protective coating 26 similar to that employed externally of the ship. By insulating the tank on the side containing the ballast water, the tank structure then will be at the same temperature as that of the adjacent ship structure and, thus, avoid problems of differential thermal contraction.

As best shown in FIG. 4, each cylindrical water ballast tank extends between the deck and the bottom of the vessel. At the bottom of the tank there is provided means for connecting the tank with the sea. The internal tank insulation 32 extends along the internal surface of the ballast tank wall terminating approximately at the neck or duct 30. Each bottom duct contains annular bearing insulation members 34 comprised of balsa wood or a similar material which correspond to the shape of the duct 30 disclosed as being cylindrical. A remotely-operated valve 36 of conventional construction is mounted within each bottom duct 30 and at the tank bottom is connected with a conduit 38 which in turn may be connected to an immersed or deep well pump 39 for filling and/or discharging water. The bottom conduit 38 and valve 36 open into a sea chest 44 incorporated in an expansion bell 42 of stainless steel or like material, which is secured between the bearing insulation members 34 as shown in FIG. 4. A strainer plate 45 is disposed across the open end of the sea chest 44 to prevent entry of undesirable particles contained in the sea water.

FIG. 4 also shows an arrangement for providing access to the ballast tank through the deck. As shown, the deck of the vessel can be constructed at predetermined locations to provide a plurality of structural domes 50, each of which operably is secured to a corresponding water ballast tank 28. A bearing insulation member 48, similar to bearing insulation 34, is disposed about each duct to provide a suitable structure for securing the dome 50, which is made from aluminum, 9 percent nickel or some other suitable metal capable of retaining suitable physical properties at moderately low temperatures and having good fatigue properties or a reinforced plastic. The dome mounts the necessary piping -52 for transferring ballast water between the tank 28 and deck-mounted facilities or conduits. A manhole 54 formed in the dome 50 provides accessto the tank interior.

While in the preferred embodiment the invention has been described as comprising cylindrical ballast tanks, it also is within the scope of this invention to employ various other configurations and arrangements. Some modifications are shown in FIGS. and 6, wherein the ballast arrangement comprises a plurality of rectangular-shaped ballast tanks 56, each being constructed between only the transverse bulkheads and a longitudinally spaced adjacent web frame 58 built into ships internal structure. As shown in FIG. 6 the water ballast tanks 56 are disposed on either side of the main longitudinal bulkhead 18. Each tank must have connections to the sea and at the deck as described above for the cylindrical tank configuration.

In order to handle the ballast, various possibilities exist. A pair of conventional immersed or deep-well pumps (not shown) can be provided in each ballast tank, one for loading and one for discharging through one or more bottom sea connections. Another approach is to utilize a single conventional immersed or deep-well pump (as shown) in each ballast tank with a suitable manifold arrangement to provide for loading and discharging through a bottom sea connection. Still yet another possibility is the use of an immersed or deep-well pump(s) in each ballast tank discharging through a bottom sea connection or through an abovedeck piping system to one or more discharge headers. Loading of the ballast from one or more main ballast pumps through an above-deck ballast piping system can be employed. Another alternate arrangement is the use of a common pumping system both for loading and supplying high pressure air for ballast discharge struction and arrangements herein illustrated and described are intended to be representative of preferred embodiments and that certain changes may be made therein without departing from the clear teachings of the invention. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.

What is claimed is:

1. A tanker for the transportation of low temperature liquid cargoes comprising, in combination,

a deck;

a hull having forward, after and intermediate cargocarrying portions;

thermal insulation secured externally to said hull in the area of said intermediate cargo-carrying portion', a longitudinal bulkhead extending for the length of said intermediate cargo-carrying portion;

transverse bulkheads spaced throughout the length of said intermediate cargo-carrying portion; said cargo-carrying portion being separated into a plurality of cargo-containing spaces formed by said longitudinal and transverse bulkheads and said hull; and

ballast tank means located at the intersection of each of said transverse bulkheads with said longitudinal bulkhead exclusively for carrying the necessary water ballast and being constructed and arranged so that said water ballast is at a different temperature from that of said liquid cargo for satisfactory operation and sea kindliness of the tanker and insulation located internally of and secured to said ballast tank means whereby said liquid cargo is in direct contact with said hull and said ballast tank means which is substantially at the temperature of said cargo.

2. A tanker according to claim 1 wherein said ballast tank means comprise a tank having a cylindrical configuration and extending vertically between the deck and the bottom of said tanker.

3. A tanker according to claim 2 wherein each of said ballast tank means includes means for connecting said tank at the top and bottom thereof to ballast handling facilities.

4. A tanker according to claim ll wherein each of said ballast tank means includes a dome secured thereto at the top, said dome and said ballast tank means being 7. A tanker according to claim 1 wherein said ballast relatively arranged so that they are subjected to differtank means includes insulation secured to the inner surent temperatures. face thereof.

5. A tanker according to claim 1 wherein said ballast 8. A tanker according to claim 1 wherein each of said tank means comprises a tank having a rectangular con- 5 ballast tank means includes means for the loading and figuration and secured between each of said transverse discharge of ballast. bulkheads and an adjacent web frame structure. 9. A tanker according to claim 1 wherein each of said 6. A tanker according to claim 5 wherein said tanks ballast tank means includes a relatively narrow duct at extend transversely of said intermediate cargo-carrying the top and bottom thereof. portion. 0 

1. A tanker for the transportation of low temperature liquid cargoes comprising, in combination, a deck; a hull having forward, after and intermediate cargo-carrying portions; thermal insulation secured externally to said hull in the area of said intermediate cargo-carrying portion; a longitudinal bulkhead extending for the length of said intermediate cargo-carrying portion; transverse bulkheads spaced throughout the length of said intermediate cargo-carrying portion; said cargo-carrying portion being separated into a plurality of cargo-containing spaces formed by said longitudinal and transverse bulkheads and said hull; and ballast tank means located at the intersection of each of said transverse bulkheads with said longitudinal bulkhead exclusively for carrying the necessary water ballast and being constructed and arranged so that said water ballast is at a different temperature from that of said liquid cargo for satisfactory operation and sea kindliness of the tanker and insulation located internally of and secured to said ballast tank means whereby said liquid cargo is in direct contact with said hull and said ballast tank means which is substantially at the temperature of said cargo.
 2. A tanker according to claim 1 wherein said ballast tank means comprise a tank having a cylindrical configuration and extending vertically between the deck and the bottom of said tanker.
 3. A tanker according to claim 2 wherein each of said ballast tank means includes means for connecting said tank at the top and bottom thereof to ballast handling facilities.
 4. A tanker according to claim 1 wherein each of said ballast tank means includes a dome secured thereto at the top, said dome and said ballast tank means being relatively arranged so that they are subjected to different temperatures.
 5. A tanker according to claim 1 wherein said ballast tank means comprises a tank having a rectangular configuration and secured between each of said transverse bulkheads and an adjacent web frame structure.
 6. A tanker according to claim 5 wherein said tanks extend transversely of said intermediate cargo-carrying portion.
 7. A tanker according to claim 1 wherein said ballast tank means includes insulation secured to the inner surface thereof.
 8. A tanker according to claim 1 wherein each of said ballast tank means includes means for the loading and discharge of ballast.
 9. A tanker according to claim 1 wherein each of said ballast tank means includes a relatively narrow duct at the top and bottom thereof. 